1. Field of Invention
This invention relates generally to global positioning systems (GPS) and, in particular, GPS systems used for emergency location of cellular handsets.
2. Description of Related Art
Various methods have been put forth in order to address the need for an emergency cellular location system. One method utilizes a number of cell transmission towers to locate a cell phone user by standard triangulation methods. This method is limited due to the low level of handset power in that it is unlikely that three or more towers will receive the signal needed for triangulation. Another method utilizes the GPS system, whereby a GPS receiver is located in the cell handset. Like the cell-tower system, this method is limited because of the lack of transmitted power, but also due to the distance of the satellite mounted transmitters from the handset receiver.